Tasks launched by tasktracker in separate JVM can't generate log output
-----------------------------------------------------------------------
Key: HADOOP-406
URL: http://issues.apache.org/jira/browse/HADOOP-406
Project: Hadoop
Issue Type: Bug
Components: mapred
Affects Versions: 0.4.0
Reporter: Chris Schneider
Child JVM's don't have access to logging config system properties. When the
child JVM gets launched, it doesn't inherit the Java system properties
hadoop.log.dir and hadoop.log.file (which are actually based on the Bash
environment variables $HADOOP_LOG_DIR and $HADOOP_LOGFILE). This means that you
get no log messages from the actual map/reduce tasks that are executing.
Stefan Groschupf reported this problem a while back:
-------------------------------------------------------------------------
To: [email protected]
From: Stefan Groschupf <[EMAIL PROTECTED]>
Subject: tasks can't log bug?
Date: Tue, 25 Jul 2006 19:26:17 -0700
X-Virus-Checked: Checked by ClamAV on apache.org
Hi Hadoop developers,
I'm confused about the way logging works within map or reduce tasks.
Since tasks are launched in a new JVM the java system properties
"hadoop.log.dir" and "hadoop.log.file" are not passed to the new JVM.
This prevents the child process from logging properly. In fact you get:
java.io.FileNotFoundException: / (Is a directory)
at java.io.FileOutputStream.openAppend(Native Method)
at java.io.FileOutputStream.<init>(FileOutputStream.java:177)
at java.io.FileOutputStream.<init>(FileOutputStream.java:102)
at org.apache.log4j.FileAppender.setFile(FileAppender.java:289)
at org.apache.log4j.RollingFileAppender.setFile(RollingFileAppender.java:165)
at org.apache.log4j.FileAppender.activateOptions(FileAppender.java:163)
at org.apache.log4j.config.PropertySetter.activate(PropertySetter.java:256)
at
org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:132)
at
org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:96)
at
org.apache.log4j.PropertyConfigurator.parseAppender(PropertyConfigurator.java:654)
at
org.apache.log4j.PropertyConfigurator.parseCategory(PropertyConfigurator.java:612)
at
org.apache.log4j.PropertyConfigurator.configureRootCategory(PropertyConfigurator.j
2006-07-25 15:59:07,553 INFO mapred.TaskTracker (TaskTracker.java:main(993)) -
Child
at
org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:415)
at
org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:441)
at
org.apache.log4j.helpers.OptionConverter.selectAndConfigure(OptionConverter.java:4
at org.apache.log4j.LogManager.<clinit>(LogManager.java:122)
at org.apache.log4j.Logger.getLogger(Logger.java:104)
at org.apache.commons.logging.impl.Log4JLogger.getLogger(Log4JLogger.java:229)
at org.apache.commons.logging.impl.Log4JLogger.<init>(Log4JLogger.java:65)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImp
at
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAcc
at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
at
org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529
at
org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235
at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:370)
at org.apache.hadoop.mapred.TaskTracker.<clinit>(TaskTracker.java:44)
at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:993)
We see several ways to solve this problem. First retrieve the properties
"hadoop.log.dir" and "hadoop.log.file" from the mother JVM and then pass them
to the child JVM as within the args parameter.
Second would be to access the environment variables "$HADOOP_LOG_DIR" and
"$HADOOP_LOGFILE" using System.getEnv (java 1.5).
Third there would be a more general solution. Taskrunner would resolve any
environment variables it found in "mapred.child.java.opts" by lookup the value
using System.getEnv().
Eg:
unix:
export MAX_MEMORY = 200
hadoop-site.xml:
<name>mapred.child.java.opts</name>
<value>-Xmx${MAX_MEMORY}</value>
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
